In recent years, in a wireless communication system such as a cellular phone, a wireless LAN, or the like, a demand for terminals usable in multi-modes or multi-bands has increased. For example, the terminals include a cellular phone having a wireless LAN function, a cellular phone usable in multi-bands, a wireless LAN device usable in multi-bands, and the like. In general, the terminals that provide the multi-modes or multi-bands essentially include an RF switching apparatus that is connected to an antenna and functions to select any one of the multiple modes or multiple bands.
FIG. 1 illustrates a schematic configuration diagram of a representative multi-band terminal. Referring to FIG. 1, a transmitter outputs signals transmission signals corresponding to two frequency bands and each transmission signal is amplified by a power amplifier and then passes through a band-pass filter (BPF) and thereafter, is transmitted through an antenna. Meanwhile, a reception signal that is received through the antenna is amplified by a low noise amplifier and transferred to a receiver. The receiver is implemented to demodulate reception signals corresponding to four frequency bands, respectively. Like this, six RF switches are connected to the antenna in order to the transmission signal or reception signal corresponding to each frequency band as shown in the figure. In addition, it is possible to transmit a transmission signal of a desired frequency band or receive a reception signal of a desired frequency band by controlling each switch.
In the multi-band terminal, insertion loss is essentially generated due to the RF switch. In general, the insertion loss generated due to the RF switch is not a big problem in the receiver. However, in the transmitter that needs to send a very high output signal, if the insertion loss increases, the output of the power amplifier needs to increase in order to maintain output power constantly. As such, if the output of the power amplifier increases, unnecessary harmonic components increase and linearity deteriorates, in particular, the power consumption of the power amplifier increases as much. Therefore, the life-span of a battery of the terminal is shortened.